This invention relates to a clamping apparatus for supporting a portable machine tool, which can be used in railroad track work and, more specifically, to support a portable rail drill which is used for the drilling of a plurality of holes adjacent the rail joint preparatory to attachment of plate to sections of rail abutting at the joints.
A clamping apparatus of the general type disclosed herein is shown in Miller U.S. Pat. No. 2,887,908 and Stougaard U.S. Pat. No. 3,706,505, owned by the assignee of this application. Miller shows a rail drill of a size and weight to be portable which is provided with a frame having legs for ground support and a clamping device for clamping it to a rail. The rail drill shown in the patent has an impositive clamping device which did not securely hold the unit to the rail during drilling of a hole.
Stougaard discloses an improved clamping structure that provides the secure gripping of a rail to hold the rail drill firmly locked in position during drilling. Means are shown for simply adjusting the rail drill unit to four different pre-set height adjustments to handle a plurality of different sized rails which provide for repeated accuracy in the height adjustment of the rail drill. Accurate alignment of the rail drill is not assured because of the clamp unit locating beam on the top of the rail ball, which is subject to wear.